A device for detecting gas and controlling volume of clean gas includes a gas detection module and a gas guider. The gas detection module includes a control circuit board, a gas detection main part and a microprocessor, wherein the gas detection main part detects a gas to generate a signal and transmits the signal to the microprocessor for calculating and processing so as to generate a gas detection data, and the microprocessor outputs a power signal and a pulse-width modulation (PWM) signal according to the gas detection data. The gas guider receives the power signal and the PWM signal outputted by the microprocessor, the gas guider is enabled or disabled, as well as a rotation speed and an output volume of clean gas of the at least one gas guider are adjusted according to the power signal and the PWM signal.